The planned opposition march in central Moscow is underway, with thousands of demonstrators reportedly streaming through central a central boulevard en route to the rally point, RIA Novosti reported.

Columns of protesters filed through the city as part of the "March of Millions," waving flags and sporting placards and slogans denouncing the Kremlin and poking fun at the leadership.

About 20,000 people have taken part in the march thus far. The demonstrators are reportedly peaceful and in good spirits.

Among the political movements in attendance are Solidarity, the People's Republican Party, Left Front, led by radical firebrand Sergei Udaltsov, as well as former opposition lawmaker Gennady Gudkov, who was dismissed from the State Duma on Friday over his alleged business activities.

Gudkov told journalists at the scene that his ouster was ordered from the Kremlin.

Anti-corruption blogger Alexei Navalny, chess champion-cum-politician Garry Kasparov and former Prime Minister Mikhail Kasyanov are also in attendance.